Clatchib



L. R. McCLATCHIE.

ELECTRIC HEATING ELEMENT.

APPLICATION FILED MAR. 4, 1916.

1 1 95,828 Patented Aug. 22, 1916.

VVYTNEESES [NVEN TUE.

J m n M YEW ISO UNITED STATES PATENT OFFICE.

LEWIS R. MOCLATCHIE, OF WESTON, ONTARIO, CANADA, ASSIGNOR TO THE MOFEAT STOVE COMPANY OF WESTON, LIMITED, 0]? WESTON, ONTARIO, CANADA.

ELECTRIC HEATING ELEMENT.

Specification of Letters Patent.

Patented Au 22, 1916.

Application filed March 4, 1916. Serial No. 82,214.

To all whom it may concern:

Be it known that I, LEWIS ROY Mo- CLATCHIE, of the town of Weston, in the county of York, Province of Ontario, Canada, a subject of the King of Great Britain, have invented certain new and useful Improvements in Electric Heating Elements, of which the following is a specification.

This invention relates to heating elements of a type particularly adapted for heating pots, kettles, pans and the like which are set over the element. To secure economy it is necessary that the heat generated be taken up as completely as possible by the pot or pan and to as small an extent as possible by the support of the resistance of the element. The ideal in efficiency is hard to attain as the support must completely shield the ele-.

ment from below to prevent losses by downward radiation, and when the element rests on the support theconduction losses are considerable.

I secure the maximum r efiiciency'compatible with reasonable cost of construction by employing as a support a grooved porcelain slab, the bottoms of the grooves being crossed by a series of integral ribs, preferably convex in cross section and curved to merge in the sides of the grooves.

The invention is hereinafter more specifically described and is illustrated in the accompanying drawings in which- Figure 1 is a planview of my improved element partly'broken' away; Fig. 2 a vertical section of the same; and Fig. 3 a cross section of part of the insulating slab illustrating more particularly the configuration of the ribs therein.

In the drawings like numerals of reference indicate corresponding parts in the different figures.

1 is a metal tray on which is supported the rectangular frame 2 of insulating material on which the resistance 8 is strung and through which the connecting wires are led. Within the frame Work a porcelain slab i is fitted, which rests on the corners 5 of the depending portion 6 of the metal tray. On the bottom of the portion 6 on the pressed up knobs 7 a sheet of asbestos or mineral wool or other heat insulating'material is supported, separated by an air space from the slab 4 and by another air space from the bottom of the pan. On top of the frame 2 the metal rim 8 is supported and-is secured to the tray 1 by suitable bolts. The parts hereinbefore described are old in the art, and my invention relates particularly to the construction and arrangement of the slab 4. This slab is formed with a series of grooves 9 in which the coils of the resistance lie. These grooves are semi-circular in cross" section at their bottoms, the radius of the semi-circle being somewhat greater than that with their sides out of contact with the sides of the grooves. The coils of the resistance are thus completely separated and insulated from one another by the material of the slab between the grooves and at the same time air may pass freely all around the coils. Vith this construction the amount of heat from the resistance which passes to the slab is materially reduced, owing to the small contact of the metal with the slab and the free air space which is provided around the coils, which allows heat which was formerly wasted to be used in heating air to pass upwardly to exert a heating effeet on the pot or pan placed over the element.

It will be understood, of course, that I do not desire to restrict myself to the specific arrangement of the ribs 10, as their construction may be considerably varied and the same result obtained.

hat I claim as my invention is:

1. In an electric heating element, a sup port for the resistance comprising a substantially solid slab of insulating material having a plurality of grooves formed therein closed below and open above, each groove having a series of closely spaced transverse ribs formed at the bottom and raised slightly above the general level of the bottom, in combination with a helical resistance coil laid in said grooves.

2. In an electric heating element, a support for the resistance comprising a slab of insulating material having a plurality of grooves formed therein, each groove having a series of transverse ribs formed at the bottonneach rib being convex in cross section to reduce its area of contact'with the resistance.

3. Inan electric heating element, a support for the resistance coils comprising a slab of insulating material having a plurality of grooves formed therein each groove having a series of transverse ribs formed at the bottom, each rib being curved substantiallyon an arc of a circle having a radius slightly greater than the radius of the coils of the resistance.

4. In an electric heating element, a support for the resistance coils comprising a slab of insulating material having a plu- I 

